Evoked potentials at varying light intensities were examined in paranoid and nonparanoid groups of schizophrenics and in rapidly cycling bipolar affective disorder patients. Early components at 100-140 milliseconds differentiated paranoid from nonparanoids but dit not change with mood cycles; late components did vary with affective mood. BIBLIOGRAPHIC REFERENCES: Buchsbaum, M. S., Post, R. M. and Bunney, W. E., Jr.: Average evoked responses in a rapidly cycling manic depressive patient. Biological Psychiatry 12: 83-99, 1977. Buchsbaum, M. S.: Psychophysiology and schizophrenia. Schizophrenia Bulletin, 3: 7-14, 1977.